Just reverse the direction that your path is drawn. If you do that, the text will be on the other side of the line.
In this case, you are using an 'S' path command with no previous path segment, so working out the reverse path is a little tricky. Here is the reverse of your sample path:
var path = snapelement.path("M 150,540 C 150,540, 150,460, 540,0")